(298h) Development of Metal-Doped Hydrotalcite Adsorbents for Rapid and High-Capacity CO2 Capture at High Temperature

Hydrotalcite (HT) has emerged as a promising candidate for CO₂ capture at elevated temperatures (200−400 °C) due to its rapid sorption-desorption kinetics and excellent regenerability. Despite these advantages, its conventional CO₂ sorption capacity remains insufficient for large-scale industrial applications, necessitating further enhancements through material modification. In this study, we reported a series of monometallic (K, Na, Li, Ga, Sc) HT and bimetallic (K-Na, K-Li, K-Ga, K-Sc) HT adsorbents with a fixed 20 wt.% metal loading via impregnation to improve CO₂ adsorption performance. The results showed that the bimetallic (K-Na)₂₀ HT adsorbent exhibited remarkable CO₂ adsorption capacity of 9.60 mmol/g at 240 °C and 1 atm, surpassing monometallic (7.50 mmol/g) and bare-HT (6.78 mmol/g) adsorbents. However, reduction in surface area (from 433 m²/g to 367 m²/g) and pore volume from 0.68 cm³/g to 0.66 cm³/g of (K-Na)₂₀ HT, indicating that the enhanced CO₂ uptake is attributed to the increased active sites of the composite as confirmed by the CO₂-TPD. Furthermore, dynamic CO₂ adsorption experiments were performed using binary, ternary, and multicomponent mixtures confirm the superior performance of (K-Na)₂₀ HT under realistic gas environment. In addition, the heat of adsorption ( for CO₂ was highest in (K-Na)₂₀ HT (68.92 kJ/mol), demonstrating stronger affinity towards CO₂ compared to bare HT (17.59 kJ/mol). Importantly, (K-Na)₂₀ HT showed excellent reusability maintaining a stable CO₂ capture capacity (~ 5 mmol/g) after an initial decline over 12 sequential sorption–desorption cycles.